This research is designed to secure information about the estrogen responsiveness of human mammary cancer. Specifically, we will pursue this objective using three approaches: (1) a scan of all the human breast cancer cell lines maintained by the EG&G Mason Research Institute for presence and inducibility by estrogen of the enzyme peroxidase, (2) investigation into the idea that histone acetylation and estrogen action are related, and (3) a probe into the concept that insulin might be involved in retention of estrogen receptors in the nucleus of human breast cancer cells. We will obtain each of the at least eleven human breast cancer cell lines available from the EG&G Mason Research Institute, and assay for peroxidase in normal serum-containing medium and then in the same medium in the presence of 1nm estradiol, all in logarithmically growing cells. These are conditions in which other estrogen-inducible proteins have previously been shown to be induced in human breast cancer cells. In order to detect a possible relationship between histone hyperacetylation (which is known to modify chromatin structure and has been implicated in gene activation) and estrogen action, we will hyperacetylate human breast cancer histones in live MCF-7 cells, using sodium butyrate, and observe any effects on binding of estrogen receptor to the nuclei and on the induction of progesterone receptor. Progesterone receptor experiments will be done with butyrate and estradiol separately and together, to test for any synergism. Finally we will investigate the relationship of insulin and estrogen action in MCF-7 cells by observing the effect of varying concentrations of insulin on nuclear retention of estrogen receptor.